Pressure regulating valves/pressure regulators are used in myriad industrial and residential applications for controlling the downstream pressure of a fluid. For example, in chemical processing plants or oil refineries, pressure regulating valves are used to manipulate a flowing fluid to compensate for increases or decreases in demand, or other load disturbances, and thus keep the fluid pressure regulated. Similarly, pressure regulating valves may be used in plumbing fixtures to maintain a pre-determined pressure of fluid that automatically adjusts to variations in demand, such as anti-scald valves in showers or faucets. By controlling downstream pressure, pressure regulating valves compensate for variations in downstream demand. For example, as downstream demand increases, pressure regulating valves open to allow more fluid to flow through the pressure regulating valve, thus maintaining a relatively constant downstream pressure. On the other hand, as downstream demand decreases, pressure regulating valves close to reduce the amount of fluid flowing through the pressure regulating valve, again maintaining a relatively constant downstream pressure.
Pressure regulating valves have trim assemblies to control and/or characterize the flow of fluid through the valve. These trim assemblies include a movable control element, such as a valve plug, a valve seat, and a cage that retains the valve plug and characterizes the fluid flow through the valve.
Pressure regulating valves can be categorized as either balanced or unbalanced. Unbalanced valves typically have high pressure inlet fluid on one side of the valve plug and lower pressure outlet fluid on the other side of the valve plug. Unbalanced valves sometimes suffer from damage that occurs to the valve seat. In unbalanced valves with high inlet pressures, the fluid pressure acting on large valve orifices can crush the valve seat. This damage may require repair or replacement. Similarly, balanced valves can also suffer from damage or wear that requires occasional maintenance or repair.
When the valve cage in certain trim assemblies needs to be removed and/or replaced, the standard removal process includes first removing a bonnet that is attached to the valve body to access the internal components, such as the trim assembly. Next, the valve plug is removed by applying force to the valve stem, which pulls the valve plug out of the cage and thus out of the valve body. Finally, the cage may be removed. In cages having thin walls, the cage often becomes stuck within the valve body, thereby necessitating tapping additional lifting holes in the cage wall for extraction. This is a very time consuming and costly process. In other valves, a build up of material, for example magnetite in high pressure bypass valves, may cause the cage to stick within the valve body.